Modular transceiver design for improved UDAR mapping

Abstract

A measurement system in a borehole in the earth's subsurface configured to measure a measurement parameter of an earth formation around the borehole. Tire measurement comprises a first transceiver configured to operate in a first transmit mode or in a first receive mode, a second transceiver configured to operate in a second transmit mode or in a second receive mode, a first switching module configured to switch the first transceiver from the first transmit mode to the first receive mode and vice versa, and a second switching module configured to switch the second transceiver from the second transmit mode to the second receive mode and vice versa, wherein in the first transmit mode the first transceiver transmits a first transmission signal into the earth formation and wherein in the first receive mode the first transceiver measures a first received signal from the earth formation.

Description

Attorney Docket No.: 65REL-510270-WO-3 (000228) MODULAR TRANSCEIVER DESIGN FOR IMPROVED UDAR MAPPING INVENTOR(S): Andreas Hartmann (DE), Kersten Kraft (DE), and Eugen Medvedev (DE) CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of co-pending U.S. Provisional Application Serial No. 63 / 613,442, filed December 21, 2023, the entirety of which is incorporated by reference herein in its entirety and for all purposes. BACKGROUND OF THE INVENTION 1. Field of Invention

[0002] The present disclosure relates to a downhole tool, and more specifically is directed to systems and methods for selectively switching two or more transceivers between different operational modes while operating downhole to map a formation adjacent to a wellbore. 2. Description of Prior Art

[0003] Well logging is an important technique used to make a detailed record in a well log which measures one or more petrophysical properties of the subterranean formations through a drilled borehole. Well logging often involves lowering a tool on the end of a wireline into a borehole, or is conducted while drilling with a logging while drilling (“LWD”) tool that mounts to a drill string. In particular, the logging tool may be incorporated in a bottom hole assembly (“BHA”) located at the lowest part of a drill string to measure resistivity in the subterranean formation to determine the fluids trapped within the subterranean formation, the depths of trapped fluid, and the type of fluid, e.g., hydrocarbon or water. Measuring formation resistivity also provides information on the presence and location of a bed boundary within the subterranean formation. The logging tool may measure formation resistivity by inducing an electrical field in the subterranean formation that has a varying potential and measuring a IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) change in potential in the wellbore, and / or may generate a primary magnetic field in the subterranean formation from a transmitter thereby inducing an eddy current in the subterranean formation. A secondary magnetic field is created by the eddy current. Thus, a combined field is measured as a resulting voltage with a receiver included with the logging tool. A drawback with existing transmitter / receiver imaging systems is they are limited in the extent of their coverage, which is dictated by their spacing and relative positioning. SUMMARY OF THE INVENTION

[0004] Disclosed herein is an example of a measurement system in a borehole in the earth’s subsurface configured to measure a measurement parameter of an earth formation around the borehole. The measurement system includes a first transceiver configured to operate in a first transmit mode or in a first receive mode, wherein in the first transmit mode the first transceiver transmits a first transmission signal into the earth formation and wherein in the first receive mode the first transceiver measures a first received signal from the earth formation. The measurement system further includes a second transceiver configured to operate in a second transmit mode or in a second receive mode, wherein in the second transmit mode the second transceiver transmits a second transmission signal into the earth formation and wherein in the second receive mode the second transceiver measures a second received signal from the earth formation. The measurement system includes a first switching module configured to switch the first transceiver from the first transmit mode to the first receive mode and vice versa. The measurement system further includes a second switching module configured to switch the second transceiver from the second transmit mode to the second receive mode and vice versa. The measurement system further includes a third transceiver configured to operate in a third transmit mode or in a third receive mode, wherein in the third transmit mode the third transceiver transmits a third transmission signal into the earth formation and wherein in the IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) third receive mode the third transceiver measures a third received signal from the earth formation. The measurement system further includes a third switching module associated with the third transceiver configured to switch the third transceiver from the third transmit mode to the third receive mode and vice versa. The distances between the first and second transceiver, the first and third transceiver, and the first and third transceiver are all different. The first transceiver includes a first antenna assembly and a second antenna assembly, wherein the first and second antenna assemblies have different directivity. The first transceiver includes a first transmission signal generator and the first switching module includes a first transmission switch configured to selectively shorten the first transmission signal generator. The first transceiver includes a first receiver signal path configured to measure the first received signal and includes first receiver signal path electronics and wherein the first switching module includes a first receiver signal path switch configured to selectively shorten the first receiver signal path electronics. The first transceiver includes a first antenna with a first antenna center tap and the first switching module includes a first center tap switch that selectively grounds the first antenna . The measurement system further includes a controller configured to instruct the first switching module to switch the first transceiver to the first transmit mode and the second switching module to switch the second transceiver to the second receive mode in a first time interval. The controller is further configured to instruct the first switching module to switch the first transceiver to the first receive mode and the second switching module to switch the second transceiver to the second transmit mode in a second time interval. The controller is further configured to determine a clock-offset corrected phase from a first phase measurement by the second transceiver in the first time interval and a second phase measurement by the first transceiver in the second time interval. The controller is further configured to determine if a variation of an offset between a first clock in the first transceiver and a second clock in the second transceiver is below a preselected variation threshold value. IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228)

[0005] Also disclosed is a method of measuring a measurement parameter of an earth formation around a borehole in the earth’s subsurface. The method includes deploying a measurement system into the borehole. The measurement system includes a first transceiver configured to operate in a first transmit mode or in a first receive mode, a second transceiver configured to operate in a second transmit mode or in a second receive mode, a first switching module configured to switch the first transceiver from the first transmit mode to the first receive mode and vice versa, and a second switching module configured to switch the second transceiver from the second transmit mode to the second receive mode and vice versa. The method further includes transmitting a first transmission signal into the earth formation from the first transceiver that is operating in the first transmit mode. The method further includes receiving a first received signal from the earth formation with the second transceiver operating in the receive mode. The method further includes switching, by the first switching module, the first transceiver to operate in the first receive mode. The method further includes switching, by the second switching module, the second transceiver to operate in the second transmit mode. The method further includes transmitting a second transmission signal into the earth formation from the second transceiver that is operating in the second transmit mode. The method further includes receiving a second received signal from the earth formation with the first transceiver operating in the first receive mode. The method further includes characterizing the measurement parameter of the earth formation around the borehole using the first received signal and the second received signal. The method further includes transmitting a third transmission signal into the earth formation from a third transceiver of the measurement system that is operating in a third transmit mode. The method further includes switching, by a third switching module of the measurement system, the third transceiver to operate in a third receive mode. The method further includes receiving a third received signal from the earth formation with the third transceiver operating in the first receive mode. The method further includes IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) characterizing the measurement parameter of the earth formation around the borehole using the first received signal, the second received signal, and the third received signal. The distances between the first and second transceiver, the first and third transceiver, and the first and third transceiver are all different. The first transceiver includes a first antenna assembly and a second antenna assembly, wherein the first and second antenna assemblies have different directivity. The first transceiver includes a first transmission signal generator, the first switching module includes a first transmission switch, and wherein switching, the first transceiver to operate in the first receive mode comprise to shorten the first transmission signal generator by the first transmission switch. The first transceiver includes a first receiver signal path configured to measure the first received signal and comprising first receiver signal path electronics and wherein the first switching module includes a first receiver signal path switch; further comprising shortening, with the first receiver signal path switch, the first receiver signal path electronics when the first transceiver is operated in the first transmit mode. The first transceiver includes a first antenna with a first antenna center tap and the first switching module includes a first center tap switch; further comprising grounding, with the first center tap switch the first antenna. The method further includes instructing, using a controller of the measurement system, the first switching module to switch the first transceiver to the first transmit mode and the second switching module to switch the second transceiver to the second receive mode in a first time interval. The method further includes instructing, using the controller of the measurement system, the first switching module to switch the first transceiver to the first receive mode and the second switching module to switch the second transceiver to the second transmit mode in a second time interval. The method further includes determining, with the controller, a clock-offset corrected phase from a first phase measurement by the second transceiver in the first time interval and a second phase measurement by the first transceiver in the second time interval. The method further includes determining, with the controller, if a IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) variation of an offset between a first clock in the first transceiver and a second clock in the second transceiver is below a preselected variation threshold value. BRIEF DESCRIPTION OF DRAWINGS

[0006] Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which:

[0007] FIG. 1 is a side sectional view of an example of a wellbore being formed through a subterranean formation with a drill string having an assembly of transceivers.

[0008] FIGS.2A-2C are side sectional views of an example of the assembly of transceivers of FIG.1 imaging the subterranean formation.

[0009] FIG.3 is a schematic example of electronics in the assembly of transceivers of FIG.1.

[0010] FIG. 4 is a side view of a portion of the drill string of FIG. 1 having transceiver antennas.

[0011] FIG. 5 is an axial view of one of the antennas of FIG. 4 and taken along lines 5-5 of FIG.4.

[0012] FIG. 6A is a schematic example of a transmitter and a receiver signal path of a transceiver of FIG.1.

[0013] FIG.6B is another schematic example of a switching module illustrating aspects of the switches.

[0014] FIG.7 is a schematic example of measurements taken with the transceivers of FIG.1. IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228)

[0015] FIG. 8 is a graph having plots of two phase measurements before and after switching operational modes.

[0016] While subject matter is described in connection with embodiments disclosed herein, it will be understood that the scope of the present disclosure is not limited to any particular embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents thereof. DETAILED DESCRIPTION OF INVENTION

[0017] The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes + / - 5% of a cited magnitude. In an embodiment, the term “substantially” includes + / - 5% of a cited magnitude, comparison, or description. In an embodiment, usage of the term “generally” includes + / - 10% of a cited magnitude.

[0018] It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228)

[0019] In a side sectional view, FIG. 1 is an example of a wellbore 10 being formed with a drilling system 12, which includes a drill string 14 with a drill bit 16 on its lower end. The wellbore 10 is being formed through a subterranean formation 18. The drilling system 12 also includes a rotary table 20 for rotating the drill string 14 and drill bit 16. An optional controller 22 for controlling drilling system 12 or portions of it is included with the drilling system 12. A transceiver assembly 24 is included with the drill string 14, which as shown includes transceivers 261-3. While three transceivers 261-3are shown, any number of transceivers can be included. In an example, the transceiver assembly 24 measures a plurality of formation resistivity values in formation 18 to determine a real-time reservoir model to make informed, proactive decisions while drilling wells. The formation resistivity of a subterranean formation is a parameter that can be measured on basis of a measurement of electrical resistance in subterranean formation 18, which represents how strongly subterranean formation 18 opposes a flow of an electric current. In an example, a subterranean formation with a low formation resistivity is indicative that the subterranean formation is porous and / or contains salty water. In another example, a subterranean formation with a high formation resistivity is indicative that the subterranean formation has a low porosity and / or contains hydrocarbon. In some embodiments, the transceiver assembly 24 may be used to obtain accurate formation resistivity measurements to detect reservoir boundaries and provide accurate formation evaluation to reduce wellbore position uncertainty. Thus, the transceiver assembly 24 provides for optimal placement and maximized reservoir performance by geosteering away from unproductive lateral sections, such as oil-water contact (OWC) or an undesired reservoir exit. As a result, the transceiver assembly 24 yields useful information to support steering decisions of optimal wellbore placement for increased production in horizontal and multilateral wells and reduced nonproduction time (NPT) by avoiding unnecessary sidetracks. IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228)

[0020] In some embodiments, some or all transceivers 261-3 selectively generate signals from within the wellbore 10, which are received by some or all of the transceivers 261-3 that are downhole. In an example, transceiver 261generates a signal to interact with a subterranean formation 18 surrounding the wellbore 10 to generate a measurement signal, such as a measured induced electromotive force (EMF), from the other two transceivers 262,3. In another example, transceiver 262 generates a signal within the wellbore 10 to interact with the subterranean formation 18 surrounding the wellbore 10 to generate a measurement signal from the other two transceivers 261,3. In another example, transceiver 263generates a signal within the wellbore 10 to interact with a subterranean formation 18 surrounding the wellbore 10 to generate a measurement signal from the from the other two transceivers 261,2. Those skilled in the art will understand that subterranean formation 18 may include one or more formation boundaries 34, such as a bed boundary, a fluid boundary (e.g., an oil-water contact), or other reservoir boundaries that may be characterized by a different formation resistivity on either side of the formation boundary. Such formation boundaries 34 may have an effect on the formation resistivity measurements and, thus, may be detectable by measurement devices, such as transceivers 261-3from the drill string 14 in wellbore 10. In particular, transceivers 261-3may be ultra deep azimuthal resistivity (“UDAR”) transceivers that send and receive signals that are transmitted many hundreds of feet within a subterranean formation 18. An example of a UDAR transceiver is found in Wessling et al., U.S. Patent Application Publication No. US 2017 / 0322339, which is incorporated herein in its entirety for all purposes. Included with the transceivers 261-3 are switching modules 281-3, which are described in more detail below, and which provide switching of the transceivers 261-3 between transmit and receive modes. As shown, transceivers 261,2 are spaced apart from one another along an axis AX of drill string 14 a distance represented by X12, transceivers 262,3are spaced apart from one another along axis AX of drill string 14 a distance represented by X23, transceiver modules 261,3 are spaced apart IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) from one another along an axis AX of drill string 14 a distance represented by X13, and transceiver 263 is spaced apart from drill bit 16 along axis AX of drill string 14 a distance represented by X3-16. Embodiments exist in which distances X12, X23, X3-16, are all the same or are different from one another, such as distance X12, being in the tens or hundreds of meters and distance X23 and / or distance X3-16 being 10 meters or less.

[0021] Side sectional views of the drilling system 12 are shown in FIGS.2A-2C, in which the transceivers 261-3are switching between send and receive modes. Referring to FIG. 2A, transceiver 261is in a transmit or send mode and is creating a magnetic field 301in the subterranean formation 18 adjacent the wellbore 10; and at the same time, transceivers 262,3 are in a receive mode and sense the magnetic field 301. Flux lines 321 of the magnetic field 301 are included. In an example, the magnetic field 301when sensed by the transceivers 262,3is altered by an interaction with the subterranean formation 18. Furthermore, the subterranean formation 18 is characterized based on an analysis of the magnetic field 301 as sensed by transceivers 262,3. In FIG.2B transceiver 261 has been switched from a send or transmit mode to the receive mode along with transceiver 263, and transceiver 262 is switched into the transmit or send mode. In the example of FIG.2B, the relative spacing of transceivers 261-3is such that the flux lines 322 of magnetic field 302 (produced by the transceiver 262 being in the transmit mode) intersect a bed boundary 34 shown in the subterranean formation 18 ahead of drill bit 16. In contrast, flux lines 321 of magnetic field 301 (FIG. 2A) did not intersect bed boundary 34 due to the spacing of transceivers 261-3when transceiver 261was in the transmit mode. In other words, the distance from transceiver 261 to formation boundary 34 is too large to create a measurable effect on sensing transceivers 261,2. The distance from transceiver 262, however, is smaller so that the magnetic field 302 that is sensed by transceivers 261,3 is affected by the presence of the formation boundary 34 so that a measurable signal is created by the receiving transceivers 261,3. In the example of FIG. 2C, further switching occurs so that transceiver 263 IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) is in the transmit mode and transceivers 261,2 are in the receive mode, which also produces flux lines 323 from a magnetic field 303 that intersects bed boundary 34. The switching between transmit / send and receive modes of the transceivers 261-3provides an advantage of identifying structure ahead of a drill bit 16 sooner, such as if the transceivers 261-3were not switchable in mode, but instead capable of only transmitting or receiving. With knowledge of a bed boundary 34 sooner by the ability to switch the transceivers 261-3 between transmit and receive mode during drilling and without stopping or removing the drill string 14 from the wellbore 10, the drill bit 16 can be redirected to avoid (or intersect) the bed boundary 34.

[0022] In some embodiments, a traditional UDAR system includes a transmitter (“TX”) module and several receiver (“RX”) modules. These modules are mounted in a BHA at different positions to achieve multiple spacings between the modules. The main goal of the traditional UDAR system is to create a rich data set to map the subterranean formation 18 surrounding the wellbore 10. The traditional UDAR system usually increases the number of modules in the BHA to increase the volume of the acquired UDAR data. In an example, the traditional UDAR system includes one transmitter module TX and three receiver modules RX1, RX2, and RX3to create readings with three spacing, such as readings of TX- RX1, TX- RX2, and TX- RX3. However, the cost of the modules in the traditional UDAR system employed in the BHA scales linearly with the volume of the acquired UDAR data. By using transceivers 261-3, instead of the traditional transmitter and receiver modules, for example by replacing traditional transmitter and receiver modules by a uniform transceiver module (“XCVR”), it is possible to generate more data with less TX / RX modules to allow the same or better measurement quality by overall reduced cost for the BHA hardware.

[0023] The XCVR system described herein provides benefits over the traditional UDAR system. In an example, a three-module XCVR configuration using the transceivers 261-3IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) obtains readings with three spacings X12, X13, X23 by switching the operational modes of the transceivers 261-3 between a transmit mode and a receive mode. Each spacing is a distance between two corresponding transceivers 261-3. In particular, the three-module XCVR configuration XCVR1, XCVR2, XCVR3(corresponding to transceivers 261, 262, 263, respectively) may be used to create readings with three spacings: a first spacing X12 using XCVR1 as a transmitter and XCVR2 as a receiver (or vice versa), a second spacing X13 using XCVR1as a transmitter and XCVR3as a receiver (or vice versa) , and a third spacing X23using XCVR2as a transmitter and XCVR3as a receiver (or vice versa). In this example, the three- module XCVR configuration reduces the cost by 25% compared to the traditional UDAR system using one transmitter module and three receiver modules to provide measurements with the same spacings between transmitters and receivers. Therefore, the three-module XCVR configuration may be used to obtain additional data without creating additional costs for modules. A further advantage is that a BHA equipped with the XCVR system has a significantly shorter length than a BHA equipped with a traditional UDAR system and provides measurements with the same spacings.

[0024] Furthermore, in usual rig operations, backup tools for each component are placed on the rig site to quickly replace a tool that failed downhole. For example, in a one-transmitter and one-receiver setting, the traditional UDAR system needs two backup tools associated with the transmitter and receiver. However, the XCVR system only needs one backup tool because the transmit / receive role of the transceivers is configurable, reducing the backup tool cost by 50%. Therefore, the XCVR system has simplified maintenance and operation because there is no difference in handling of the modules in various hardware, operational, and maintenance procedures. The only difference is the software configuration to assign the transmit / receive role of the transceivers in the BHA. In an example, a fixed role setting is used in a first BHA and programmed prior to deployment. In another example, an automated, self-configuring IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) system is used in a second BHA. Thus, the XCVR system may be used for fleet optimization to reduce the fleet size and number of backup tools needed on the rig site.

[0025] In some embodiments, the traditional UDAR system is configured to implement a transmitter ahead configuration, examples of which have a spacing ranging from about 10 meters (m) to about 30 m from the drill bit 16 to the transmitter. In an example, there is a spacing of about 10 m from XCVR1 to XCVR2. In another example, there is a spacing of about 30 m from XCVR1to XCVR3. In another example, there is a spacing of about 30 m from XCVR1to the drill bit 16 and / or spacing in the range of 1 m – 20 m (such as 1 m – 10 m or even 1 m – 4 m) from XCVR3 to the drill bit 16. In particular, the traditional UDAR system places the short spacing close to the drill bit 16 on the drill string 14. By using the three-module XCVR configuration and switching the XCVR2(that is between upper-end transceiver XCVR1and lower-end transceiver XCRV3) to a transmit mode, the difference reading of XCVR2– XCVR1 geometrically focuses the measurement to look aside, which is beneficial for geosteering. Furthermore, when a transmitter fails, the XCVR system allows switching to a different XCVR for a limited continued operation without the need to pull out of the hole (POOH) which would be the consequence if the transmitter fails in a traditional UDAR system.

[0026] Referring now to FIG. 3, shown is a schematic example of components in the transceivers 261-3 of the transceiver assembly 24 (FIG. 1) that each may include one or more of a Z antenna 36, an X antenna 38, and a Y antenna 40 connected to their respective transceiver electronic units XCVR X, XCVR Y, and XCVR Z that include the switching modules 281-3. The terms “X antenna,” “Y antenna,” and “Z antenna” generally refer to a directivity of the antennas 36, 38, and 40. For example, if antennas 36, 38, and 40 are multipole antennas (e.g., dipole antennas) creating (oscillating) multipole (e.g., dipole) electric / magnetic fields, the labels “X”, “Y”, and “Z” typically refer to the direction of the axis of symmetry of the IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) corresponding multipoles (e.g., dipoles). In an example, one of the transceivers 261-3 is configured to generate a magnetic field in a subterranean formation 18 and induces a magnetic field response that is measured by the other two transceivers. In particular, the transceivers 261-3are placed in a housing incorporated as or in a downhole component, such as a drill string section, a drilling pipe, or a drilling collar. The housing is optionally made from an electrically conducting material, such as steel. All transceivers 261-3 are shown connected to a common downhole power / communication bus system (“DBS”) via a controller (“CONTROLLER”) and a DBS communication module 39. In the DBS communication module 39 are acquisition control, data processing, decoupling of DBS communication, and breaker control. The DBS communication module 39 may be part of the controller (“CONTROLLER”) or may be a separate electronic device. In the transceiver electronic units XCVR X, XCVR Y, and XCVR Z and / or the controller (“CONTROLLER”), there is signal generation and power amplifier, data acquisition, transmit mode / receive mode switching, and processing (binning and compensation). Also included is synchronization, which involves creating sync signals, recovering clock and trigger from sync signals, and providing master clock and trigger. A toolface angle measurement device (such as a magnetometer, an accelerometer, or a gyroscope, “MAGNETOMETER”) acquires toolface angle and distributes it to the controller (“CONTROLLER”) and other portions of the transceiver electronics. The memory (“MEMORY”) stores raw and / or processed data from the controller (“CONTROLLER”), and there is memory dump (such as a high speed dump, e.g., via Ethernet) over a dump port (not shown). A power supply (not shown) provides voltages for analog and digital circuits.

[0027] Shown in a side elevational view in FIG.4 is a portion of the drill string 14 having the X antenna 38 and Y antenna 40. Also shown is the Z antenna 36, which can be mounted onto a sub, and is made up of a coil of wires arranged to circumscribe axis AXof drill string 14. In the embodiment of FIG.4, X antenna 38, and Y antenna 40 are mounted on sub 48 adjacent to IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) Z antenna 36, and each includes coils 50 and 52 having wires 54 and 56 that are oriented generally parallel with axis AX. In the example shown, X antenna 38 and Y antenna 40 are disposed at substantially the same axial location on the sub 48 but angularly spaced apart (e.g., spaced 90° apart) from one another around the circumference of sub 48. FIG. 5 is a sectional view of X antenna 38 and Y antenna 40 of FIG. 4 taken along lines 5-5, which includes an antenna core and a cover 62, such as a polyether ether ketone (“PEEK”) cover. In this example, a first and second X antenna 381, 2are disposed roughly 180° from one another, and a first and second Y antenna 401, 2are disposed roughly 180° from one another. It should be pointed out that in the example of FIGS. 2A-2C the orientation of the magnetic fields 301-3 and flux lines 321-3 are subject to which of the Z antenna 36, X antenna 38, or Y antenna 40 is used to generate the particular one of the magnetic fields 301-3. In an example, an axis of symmetry of a magnetic field generated by a Z antenna 36 will be orthogonal to an axis of symmetry of a magnetic field generated by an X antenna 38, which in turn will be orthogonal to an axis of symmetry of the magnetic field generated by an Y antenna 40. A further advantage of the switching ability disclosed herein is to obtain more views due to the ability to switch to differently oriented antennas, and to quickly obtain those views.

[0028] Referring now to FIG.6A, shown is a schematic 64 of the switching modules 28i (such as transceiver electronics 28i) where the index i stands for 1, 2, or 3 to reflect the three transceiver configuration as shown in FIG.1 or a higher number if more than three transceivers are used. Portions of the switching modules 28ishown in FIG.6A may be part of the transceiver electronic units XCVR X, XCVR Y, and XCVR Z as shown in FIG.3. The switching modules 28i allow for a transition between the transmit and receive modes of the Y antenna 40, X antenna 38, and Z antenna 36. In an example, the switching modules 28i (such as transceiver electronics 28i) include a configurable broadband impedance matching network for reconfiguring operations of the two or more UDAR transceivers between different operational IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) modes. In FIG.6A, a receiver signal path 66 shown in dashed outline) illustrates a signal path from an RX protection device (“RX Protection”) to an analog to digital converter (“ADC RX”), via an amplifier (such as a low noise amplifier “LNA”), and a filter (“RX filter”). A micro controller unit (“MCU”) that may include a digital signal processor and a field-programmable gate array is applied to process signals and aggregate data for control, data acquisition, and processing. One or more communication lines (“COM”), for example to enable controller area network (“CAN”) communication, are used to allow communications to and / or from transceiver electronic units XCVR X, XCVR Y, XCVR Z external of the switching modules 28i. Furthermore, the switching modules 28i alternatively implement antennas in a wide band matching system using an impedance transformer, active temperature drift compensation, dynamic range antenna signal, such as one with a high dynamic antenna signal range capability (120dB minimum), and noise density of LNA less than 10nV / sqrt(Hz) to achieve performance of over 100dB for common mode rejection ratio (CMRR) and power supply rejection ratio (PSRR).

[0029] Further in the example of FIG. 6A, a transmitter signal path 68 (shown in dashed outline) illustrates a signal path that includes a current measurement transformer 67, a filter (“TX FILTER”), a power amplifier (“POWER AMPLIFIER”), and a switching device (“CHANNEL SW”) that allows to switch transceivers 26i from a transmit mode to a receive mode (where the index i stands for 1, 2, or 3 to reflect the 3 transceiver configuration as shown in FIG.1 or a higher number if more than 3 transceivers are used). When the transceiver 26iis switched by the switching device (“CHANNEL SW”) into the receive mode, as shown by receiver signal path 66, a (broadband) signal is received by the antenna (“ANTENNA ASSEMBLY”), e.g., the Z antenna 36, the X antenna 38, or the Y antenna 40 as shown in FIG. 3) and will be passed through the RX protection device (“RX Protection”), amplified by the amplifier (“LNA”), filtered by filter (“RX filter”) and converted to a digital signal by the analog IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) to digital converter (“ADC RX”) before it is fed into the micro controller unit (“MCU”) for further processing and determination of the magnitude of the signal (e.g., the voltage or current of the signal). In the receive mode the micro controller unit (“MCU”) may also receive an additional receiver compensation or calibration signal that will be generated by the compensation signal source (“CSS”) and coupled (for example, by the current measurement transformer 67 or a separate transformer) into the receiver signal path 66. The receiver compensation signal is a known signal that can be used to compensate for temperature or drifts that may alter the signals and their measurement by the electronics of transceivers 26i. An example of a compensation / calibration apparatus and method for a downhole electric measurement is found in Folberth et al., U.S. Patent No. US 7,141,981, which is incorporated herein in its entirety for all purposes. When the transceiver 26iof FIG. 6A is switched by the switching device (“CHANNEL SW”) into the transmit mode, as shown by transmitter signal path 68, a (broadband) signal is generated by the micro controller unit (“MCU”) that will be amplified by the power amplifier (“POWER AMPLIFIER”), filtered by the filter (“TX FILTER”), and injected into the antenna (“ANTENNA ASSEMBLY”, e.g., the Z antenna 36, the X antenna 38, or the Y antenna 40 as shown in FIG.3). In this mode, the switching modules 28i receive a high input power (such as up to 15-watt (W), or even higher, for example up to 30 W or even up to 50 W) from the power / communication bus system (“DBS”). In this example, the power amplifier (“POWER AMPLIFIER”), which may be digital full bridge amplifier, is capable of amplifying signals with several signal frequencies (for example, two frequencies or more, such as up to eight frequencies or even up to 20 frequencies). Via the current measurement transformer 67 the signal in the transmit mode will also be coupled into transmitter measurement circuit where the signal (for example, the voltage or the current of the signal) will be filtered by an electronic filter (“TX Measurement Filter”) and measured (e.g. by converting it to a digital signal by an analog-digital-converter (“ADC CURRENT”) and IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) processed by the micro controller unit (“MCU”) to determine the magnitude of the voltage or current of the signal in the transmit mode with high accuracy (for example, 5% or better such as 1% or better or even 0.2% or better). Also in the transmit mode, an additional compensation or calibration signal will be generated by a compensation signal source (“CSS”) and coupled (for example, by the current measurement transformer 67 or a separate transformer) into the transmitter signal path 68. The compensation signal is a known signal that can be used to compensate for temperature or drifts that may alter the signals and their measurement by the electronics of transceivers 26i. An example of a compensation / calibration apparatus and method for a downhole electric measurement is found in Folberth et al., U.S. Patent No. U.S. 7,141,981, which is incorporated herein in its entirety and for all purposes. In the transmit mode and the receive mode the signals may be transmitted and received via a single antenna (“ANTENNA ASSEMBLY”) that may be one of the Z antenna 36, the X antenna 38, or the Y antenna 40 as shown in FIG. 3 and via the transmitter signal path 68 and the receiver signal path 66, respectively. The switching device (“CHANNEL SW”) is configured to switch from the transmit mode to the receive mode and vice versa, wherein in the transmit mode high transmitter currents will be passed to the antenna (“ANTENNA ASSEMBLY”) while protecting the sensitive electronics in the receiver signal path 66 from the impact of such high transmitter currents and wherein in the receive mode the relatively small signals from the antenna (“ANTENNA ASSEMBLY”) can be measured with high precision and accuracy without interference from the relatively high transmitter currents.

[0030] In an example of the operation of the transceiver 261-3, an instruction is received by the controllers (“CONTROLLER”) of the transceiver 261-3 to switch transceiver 261 into transmit mode and transceiver 262,3 into receive mode. In response, controller (“CONTROLLER”) of transceiver 261configures the switching module 281to put transceiver 261into transmit mode and controllers (“CONTROLLER”) of transceivers 262,3 configure the switching module 282,3 IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) to put transceivers 262,3 into receive mode. The controller (“CONTROLLER”) on the transceiver 261 causes the micro controller unit (“MCU”) of transceiver 261 to create a signal to be transmitted via the antenna (“ANTENNA ASSEMBLY”) of transceiver 261. The signal leaves the antenna (“ANTENNA ASSEMBLY”) of transceiver 261and is received at the antenna (“ANTENNA ASSEMBLY”) of the transceiver 262,3. The micro controller units (“MCU”) of transceiver 262,3 further process the signal to extract measurement data from the received data. Controller (“CONTROLLER”) of transceiver 261may cause antennas of different directivity (such as the Z antenna 36, the X antenna 38, or the Y antenna 40) to transmit signals simultaneously or sequentially. Likewise Controller (“CONTROLLER”) of transceiver 262,3 may cause antennas of different directivity (such as the Z antenna 36, the X antenna 38, or the Y antenna 40) to receive signals simultaneously or sequentially . Controller(s) (“CONTROLLER”), on one or more of transceivers 261-3, is(are) configured to combine all the measurement data into a combined measurement. For example, the combined measurement may include one or more of the magnitude / phase of the transmitted signal by transceiver 261and magnitude / phase of the received signals by transceivers 262,3. In addition, information about the directivity of the antennas (e.g., the information whether the Z antenna 36, the X antenna 38, and / or the Y antenna 40 were used) may be used to generate the combined measurements. In another example, as drill string 14 is rotating, an X antenna will become a Y antenna when the tool is rotated by 90°. So that, at transceiver 261, only a Z antenna and an X antenna, or a Z antenna and a Y antenna are needed. At transceivers 262,3, the Z antenna and both the X antenna and the Y antenna may be used to generate the combined measurements. For example, the combined measurement may comprise one or more of the magnitude / phase of the transmitted signal by transceiver 261 and magnitude / phase of the received signals by transceivers 262,3. In addition, information about the directivity of the antennas (e.g., the information whether the Z antenna 36, the X antenna 38, and / or the Y antenna 40 were used) IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) may be used to generate the combined measurements. In another example, as drill string 14 is rotating, an X antenna will become a Y antenna when the tool is rotated by 90°, so that, at transceiver 261, only a Z antenna and an X antenna, or a Z antenna and a Y antenna are needed. At transceivers 262,3side, the Z antenna and both the X antenna and the Y antenna may be used to generate the combined measurements. A coupling tensor is optionally generated to describe nine possible components (or transmitter / receiver combinations): XX, XY, XZ, YX, YY, YZ, ZX, ZY, ZZ. Over tool face angle this looks roughly like this: when toolface= 0°, X-transmitter provides XX, XY, XZ components; when toolface = 90°, X-transmitter turns into Y-transmitter and provides YX, YY, YZ components. In some embodiments, transceivers 261-3 are programmed to operate according to a predefined sequence so that when one switches from transmit to receive mode, a transceiver previously in receive mode switches into transmit mode. In general, a processing unit configures the hardware to operate in transmit or receive mode. Another option would be that both modes are active at the same time, but only one is used. Alternatively, active at the same time and being used, for instance, if transmission and reception are on different frequencies.

[0031] FIG. 6B illustrates further aspects of the switching modules 28ishowing in particular aspects of the switching device (“CHANNEL SW”). Like in FIG. 6A, FIG. 6B shows a transmitter signal path 68 and a receiver signal path 66 corresponding to transmitter signal path 68 and receiver signal path 66 in FIG. 6A. In the configuration of FIG. 6B, switching device (“CHANNEL SW”) of FIG.6A is implemented by various switches. A first switch is included in the transmitter signal path 68 to switch off or on the transmitter signal generation (“TRANSMITTER SIGNAL GENERATION”) to provide for the receive or transmit mode, respectively. In FIG. 6A, this may be included in an amplifier stage of the transmitter signal generation (“TRANSMITTER SIGNAL GENERATION”) and / or in a switchable matching network (“SMN”) but it can also be implemented in other portions of the transmitter signal IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) generation circuit (for example, in the micro controller unit “MCU”, see FIG. 6A). The switchable matching network (“SMN”) is configured to selectively match impedances to transmit signals with one or more preselected frequencies. A second switch (“TX Short”) is included in the transmitter signal path 68 to selectively shorten the transmitter signal generation. For example, when transceiver 26i is in a receive or transmit mode, the second switch (“TX Short”) can be closed opened, respectively. By closing the second switch (“TX Short”) in a receive mode, the output impedance of the transmitter signal generation will be shortened to avoid that a portion of received signal will be dampened by the output impedance of the transmitter signal generation which would reduce the sensitivity of the received signal measurement. A third switch 65 is included to selectively shorten the secondary side of the antenna impedance transformer 63. The antenna impedance transformer 63 couples the signals from the TX signal generation and / or the antenna into the receiver signal path 66. In a transmit mode, these signals can be relatively high and therefore the third switch 65 can be closed to shorten the secondary side of the antenna impedance transformer 63 to protect the amplifier (“LNA”) and other electronic equipment from these high voltage / currents. Advantageously, as shown, the primary side of transformer 63 utilizes two primary windings P1 and P2 wherein the number of windings of the two primary windings P1 and P2 together is lower than the number of windings of the secondary winding S of the transformer 63. The same may be true for the transformer 67 that advantageously may be realized with two primary windings P1 and P2 that together have a number of windings that is lower than the number of windings of the secondary winding S2 of transformer 67. For example, the ratio of the number of windings of the primary coils to the number of windings of the secondary coils of transformers 63 and / or 65 may be in the range of 1:2 or higher (such as 1:10 or higher, for example 1:25 or higher, or even 1:40 or higher). In addition, a fourth switch 69 may be included into the amplifier (“LNA”) to shut off its operation in transmit mode for further protection against the relatively IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) high signals from the antenna impedance transformer 63 in the transmit mode. A fifth switch 61 may be included when the antenna (“ANTENNA ASSEMBLY”) includes a center tap for common mode rejection. An example of such an antenna and its use for a downhole electric measurement is found in Kirchmeier et al., U.S. Patent No. US 10,416,337, which is incorporated herein in its entirety for all purposes. Such antennas are grounded for better performance in a receive mode. However, in a transmit mode such grounding would be counterproductive. Accordingly, in a transmit mode the fifth switch 61 opened or closed when transceiver 26iis in a transmit or receive mode, respectively. Those skilled in the art will understand that one, some, or all of the switches described above are electronic switches that can be operated (i.e., switched) by electronic instructions such as computer or firmware implemented instructions or digital communication to or from electronic hardware.

[0032] In an example of operating three transceiver modules, certain results are achieved as the depth of investigation varies based on the spacing between the transmitter and the receiver. Typically, the larger the spacing and lower the frequency, the larger the volume that is investigated. A combination of measurements is advantageous. As an example, using three transceiver modules 702, 704, and 706 in the BHA 700 is schematically illustrated in FIG. 7. As shown, BHA 700 comprises a first transceiver 702, a second transceiver 704, and a third transceiver 706. Between first, second, and third transceivers 702, 704, 706 are other downhole tools included such as but not limited to a drill bit (“BIT”), a steering tool (“SU”) to steer the trajectory of the wellbore that is to be drilled, a telemetry tool (“TEL”) configured to communicate with equipment at the earth’s surface and measurement tools (“LWD”) configured various parameter of the formation around the wellbore. In an example of operation of BHA 700, a first measurement 712 is obtained from a signal which is sent from transceiver module 702 and received by transceiver module 704. Likewise, a second measurement 714 is obtained from a signal which is sent from transceiver module 702 and received by transceiver IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) module 706. A third measurement 716 is obtained from a signal which is sent from transceiver module 704 and received by transceiver module 706. A fourth measurement 718 is obtained from a signal which is sent from transceiver module 704 and received by transceiver module 702. The first measurement 712 has the shallowest depth of detection (DOD) or depth of investigation (DOI) and the highest spatial resolution along the wellbore 10. The second measurement 714 has a large DOD / DOI but less spatial resolution. The third measurement 716 has a medium DOD / DOI and resolution. As a result, an improved mapping technique (“MT”) is implemented to determine measurements of phase delay and magnitude or amplitude by using the second and third measurements 714 and 716 based on Equations 1 and 2 below. The improved MT advantageously provides measurements with large DOD / DOI and good spatial resolution. For Phase: 13 23 (1)For Magnitude: 23 / 13 (2)

[0033] In equations (1) and (2), 13 denotes a phase delay (also known as phase difference)between the transmitted signal of transceiver 702 and the received signal of transceiver 706which is measured by the second measurement 714. Accordingly, 23 denotes a phase delaybetween the transmitted signal of transceiver 704 and the received signal of transceiver 706which is measured by the third measurement 716. 23 denotes an amplitude or magnitudeof the signal received by the transceiver 706 relative to the amplitude or magnitude of the signal transmitted by the transceiver 704 which is measured by the third measurement 716.Accordingly, 13 denotes an amplitude or magnitude of the signal received by thetransceiver 706 relative to the amplitude or magnitude of the signal transmitted by the transceiver 701 which is measured by the second measurement 714. Another advantage addresses the high-quality phase measurement (also known as phase delay measurements or IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) phase difference measurements). In some embodiments, transceivers 702, 704, and 706 have separate clocks that run at the same speed but may have a clock offset . When transceiver 702 is in a transmit mode and transceiver 704 is in a receive mode, the transmitter and receiverpair is used to measure a total phase delay 12 by the first measurement 712, the result maybe biased by a bias phase delay of associated with the clock offset of transceiver 702 in transmit mode and transceiver 704 in receive mode. Likewise, when switching transceiver 702 and transceiver 704, thus, transceiver 704 is in a transmit mode and transceiver 702 is in a receive mode, the switched transmitter and receiver pair is optionally used to measure a totalphase delay 21 , which is a phase delay between the transmitted signal of transceiver 704and the received signal of transceiver 702 which is measured by the fourth measurement 718.21 is then biased with the same bias phase delay of but with an opposite sign. Thisleads to the following set of equations:21 (4)where 12 is the phase delay between the transmitted signal of a first transceiver, such astransceiver 702 and the received signal of a second transceiver, such as transceiver 704, 21is the phase delay between the transmitted signal of the second transceiver and the received signal of the first transceiver, is the transmitting frequency, is the clock offset between the first transceiver clock and the second transceiver clock, is the phase delay that is generated by the formation between the first transceiver and the second transceiver (formation phase). By adding equations 3 and 4, a clock-offset corrected phase measurement is achieved: 12 21 2 (5)IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228)

[0034] Therefore, the clock-offset corrected formation phase delay may be determined byswitching a transmitter and receiver pair to measure 12 by the first measurement and21 by the second measurement and determine the formation phase delay by equation 5.FIG.8 is an example of two phase measurements before and after switching operational modes.In an example, a first phase measurement 13 802 is the phase delay in degree as a functionof measured depth (MD) in meter (m) when the first transceiver is in a transmit mode and thethird transceiver is in a receive mode. A second phase measurement 31 804 is the phasedelay when the third transceiver is in a transmit mode and the first transceiver is in a receive mode. Thus, the bias phase delay associated with the clock offset of the first transceiver clock and the third transceiver clock may be calculated by using the difference 806 of the firstphase measurement 13 802 and the second phase measurement 31 804 that isaccording to equations (3) and (4) equivalent to twice the bias phase delay . In particular, at X650 m MD, the difference 806 and therefore the bias phase delay associated with the clock offset between the first transceiver clock and the third transceiver clock has a jump which is associated with a temporary change in the clock offset due to a configuration change. Despite of that jump at around X650 m MD, the difference 806 and therefore the bias phase delay appears to be fairly constant (i.e., the variation of the bias phase delay is below a preselected bias phase delay threshold) confirming the assumption of a relatively constant clock offset during the logging of the depth interval of X700 m MD to about X200 m MD. Hence, the difference 806 allows to identify in which depth intervals the assumption of a constant phase delay is justified. Also, the determination of the bias phase delay by the difference 806 allows to determine at which time and / or depth intervals are low enough, for example below a preselected bias phase delay threshold. By periodically checking (e.g., every preselected time or depth interval) the difference 806 and / or the bias phase delay, phase measurements with a too high bias phase delay can be eliminated or corrected. This improves IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) phase accuracy and removes the necessity of measuring the clock offset. Likewise, the formation phase delayassociated with the wellbore 10 at MD in the range from X600 m toX200 m can be determined by summing the first phase measurement 13 802 and the secondphase measurement 31 804 according to equation (5). The determined formation phaseoffers accurate formation evaluation for the reservoir rock and the fluid distant from the wellbore 10 during drilling, completion, and workover operations. In an example, the determined formation phasemay be used for early detection of a reservoir boundary, such as an oil-water contact (OWC) or an undesired reservoir section, to reduce wellbore position uncertainty. In another example, the determined formation phase may be used to determine an optimal wellbore placement plan for geosteering to maximize reservoir performance for horizontal wells and multilateral wells.

[0035] In some embodiments, the improved MT generates inversion models from a plurality of UDAR measurements in both resistive and conductive environments. The service creates 2D / 3D maps of lithological and fluid boundaries for a clearer interpretation of the reservoir environment. These detailed maps provide better reservoir definition than conventional logging-while-drilling geo-steering technologies. The improved MT introduces several industry firsts, including a transceiver designed to deliver unprecedented operational flexibility to objective-driven BHA design. In addition, the industry’s first three-component collocated, and orthogonal antennas yield a higher signal-to-noise output compared to other UDAR antenna designs. While many geo-mapping technologies deliver inversion maps that claim detection depths of hundreds of feet, they do not address the key challenge of quantifying the confidence in the inversion result. The improved MT may greatly improve the capability of unlocking dynamic depth of detection up to 300 feet, boundary and resistivity confidence analysis, and statistical distribution analysis of the hybrid inversion to deliver quantifiable confidence embedded within the inversion map. The improved MT may be used for appraising IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) field production and recovery potential to support geo-steering and geo-mapping objectives. Thus, the improved MT reduces field development costs compared to conventional methods, provides a richer UDAR dataset for deeper reservoir insights, and enhances real-time decision- making to maximize reservoir contact and optimize future field development.

[0036] In some embodiments, the improved MT introduces the industry’s first transceiver modules that deliver unprecedented operational flexibility to facilitate the objective-driven design of the BHA. It also introduces the industry’s first three-component collocated and orthogonal antennas for improved signal-to-noise ratio compared to other UDAR antenna designs. These technology differentiators help MT unlock dynamic depth of detection up to 300 ft, boundary and resistivity confidence analysis, and statistical distribution analysis of the hybrid inversion. The resulting inversion map is embedded with quantifiable confidence that supports both geo-steering and geo-mapping objectives. The improved MT enables a step- change in field development by providing operators with sharper insights into reservoir distribution and quality. The improved MT may be used for appraising field production and recovery potential to identify in-fill targets and fluid contacts. It also reduces field development costs compared to conventional methods that often require the drilling of numerous appraisal wells. The richer UDAR dataset delivers a deeper understanding of the reservoir and simultaneously enhances real-time decision-making, helping to maximize reservoir contact during drilling and affording opportunities to optimize future field development. The improved MT may be implemented in various configurations in the BHA to provide greater telemetry flexibility, depending on measurement goals. These configurations help to achieve the operator’s geo-steering and geo-mapping objectives during an extensive offshore field-testing program with both standard mud-pulse and wired pipe telemetries. IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228)

[0037] In some embodiments, the improved MT enables more efficient reservoir interpretation, improved collaboration, and informed development decisions. The clarity and conciseness of the resulting inversion maps allow both domain and non-domain experts to confidently interpret the reservoir by removing perception bias. Operators can simultaneously make real- time decisions that maximize reservoir contact while setting the field up for future successes with optimized development of previously unexplored reservoir sections. The improved MT may be used for appraising field production and recovery potential to identify in-fill targets and fluid contacts. It also reduces a field’s development costs compared to conventional methods that call for drilling numerous appraisal wells. Fewer appraisal wells translate to a lower carbon footprint, thanks to significantly reduced rig time and a minimal number of trips for rig crews, supplies, and ancillary equipment to and from the offshore drilling site. The richer UDAR dataset provided by MT delivers a deeper understanding of both the near and far features of the reservoir. At the same time, it provides greater confidence in both net-to-gross and hydrocarbon-in-place estimates for enhanced real-time decision-making to maximize reservoir contact and optimize future field development.

[0038] The present invention described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. IM-#10588002.1

Claims

Attorney Docket No.: 65REL-510270-WO-3 (000228) CLAIMS What is claimed is:

1. A measurement system in a borehole in the earth’s subsurface configured to measure a measurement parameter of an earth formation around the borehole, the measurement system comprising: a first transceiver configured to operate in a first transmit mode or in a first receive mode, wherein in the first transmit mode the first transceiver transmits a first transmission signal into the earth formation and wherein in the first receive mode the first transceiver measures a first received signal from the earth formation; a second transceiver configured to operate in a second transmit mode or in a second receive mode, wherein in the second transmit mode the second transceiver transmits a second transmission signal into the earth formation and wherein in the second receive mode the second transceiver measures a second received signal from the earth formation; a first switching module configured to switch the first transceiver from the first transmit mode to the first receive mode and vice versa; and a second switching module configured to switch the second transceiver from the second transmit mode to the second receive mode and vice versa.

2. The measurement system of Claim 1, further comprising: a third transceiver configured to operate in a third transmit mode or in a third receive mode, wherein in the third transmit mode the third transceiver transmits a third transmission signal into the earth formation and wherein in the third receive mode the third transceiver measures a third received signal from the earth formation; and a third switching module associated with the third transceiver configured to switch the third transceiver from the third transmit mode to the third receive mode and vice versa.

3. The measurement system of Claim 2, wherein the distances between the first and second transceiver, the first and third transceiver, and the first and third transceiver are all different.

4. The measurement system of Claim 1, wherein the first transceiver comprises a first antenna assembly and a second antenna assembly, wherein the first and second antenna assemblies have different directivity. IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) 5. The measurement system of Claim 1, wherein the first transceiver comprises a first transmission signal generator and the first switching module comprises a first transmission switch configured to selectively shorten the first transmission signal generator.

6. The measurement system of Claim 1, wherein the first transceiver comprises a first receiver signal path configured to measure the first received signal and comprising first receiver signal path electronics, and wherein the first switching module comprises a first receiver signal path switch configured to selectively shorten the first receiver signal path electronics.

7. The measurement system of Claim 1, wherein the first transceiver comprises a first antenna with a first antenna center tap and the first switching module comprises a first center tap switch that selectively grounds the first antenna.

8. The measurement system of Claim 1, further comprising a controller configured to: instruct the first switching module to switch the first transceiver to the first transmit mode and the second switching module to switch the second transceiver to the second receive mode in a first time interval; and instruct the first switching module to switch the first transceiver to the first receive mode and the second switching module to switch the second transceiver to the second transmit mode in a second time interval.

9. The measurement system of Claim 8, wherein the controller is further configured to determine a clock-offset corrected phase from a first phase measurement by the second transceiver in the first time interval and a second phase measurement by the first transceiver in the second time interval.

10. The measurement system of Claim 8, wherein the controller is further configured to determine if a variation of an offset between a first clock in the first transceiver and a second clock in the second transceiver is below a preselected variation threshold value.

11. A method of measuring a measurement parameter of an earth formation around a borehole in the earth’s subsurface, the method comprising: a. deploying a measurement system into the borehole, the measurement system having a first transceiver configured to operate in a first transmit mode or in a first receive mode, a IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) second transceiver configured to operate in a second transmit mode or in a second receive mode, a first switching module configured to switch the first transceiver from the first transmit mode to the first receive mode and vice versa, and a second switching module configured to switch the second transceiver from the second transmit mode to the second receive mode and vice versa; b. transmitting a first transmission signal into the earth formation from the first transceiver that is operating in the first transmit mode; c. receiving a first received signal from the earth formation with the second transceiver operating in the receive mode; d. switching, by the first switching module, the first transceiver to operate in the first receive mode; e. switching, by the second switching module, the second transceiver to operate in the second transmit mode; f. transmitting a second transmission signal into the earth formation from the second transceiver that is operating in the second transmit mode; g. receiving a second received signal from the earth formation with the first transceiver operating in the first receive mode; h. characterizing the measurement parameter of the earth formation around the borehole using the first received signal and the second received signal.

12. The method of Claim 11, further comprising: transmitting a third transmission signal into the earth formation from a third transceiver of the measurement system that is operating in a third transmit mode; switching, by a third switching module of the measurement system, the third transceiver to operate in a third receive mode; receiving a third received signal from the earth formation with the third transceiver operating in the first receive mode; characterizing the measurement parameter of the earth formation around the borehole using the first received signal, the second received signal, and the third received signal.

13. The method of Claim 12, wherein the distances between the first and second transceiver, the first and third transceiver, and the first and third transceiver are all different. -31- IM-#10588002.1Attorney Docket No.: 65REL-510270-WO-3 (000228) 14. The method of Claim 11, wherein the first transceiver comprises a first antenna assembly and a second antenna assembly, wherein the first and second antenna assemblies have different directivity.

15. The method of Claim 11, wherein the first transceiver comprises a first transmission signal generator, the first switching module comprises a first transmission switch, and wherein switching, the first transceiver to operate in the first receive mode comprise to shorten the first transmission signal generator by the first transmission switch.

16. The method of Claim 11, wherein the first transceiver comprises a first receiver signal path configured to measure the first received signal and comprising first receiver signal path electronics and wherein the first switching module comprises a first receiver signal path switch; further comprising shortening, with the first receiver signal path switch, the first receiver signal path electronics when the first transceiver is operated in the first transmit mode.

17. The method of Claim 11, wherein the first transceiver comprises a first antenna with a first antenna center tap and the first switching module comprises a first center tap switch; further comprising grounding, with the first center tap switch the first antenna.

18. The method of Claim 11, further comprising: instructing, using a controller of the measurement system, the first switching module to switch the first transceiver to the first transmit mode and the second switching module to switch the second transceiver to the second receive mode in a first time interval; and instructing, using the controller of the measurement system, the first switching module to switch the first transceiver to the first receive mode and the second switching module to switch the second transceiver to the second transmit mode in a second time interval.

19. The method of Claim 18, determining, with the controller, a clock-offset corrected phase from a first phase measurement by the second transceiver in the first time interval and a second phase measurement by the first transceiver in the second time interval.

20. The method of Claim 18, determining, with the controller, if a variation of an offset between a first clock in the first transceiver and a second clock in the second transceiver is below a preselected variation threshold value. IM-#10588002.1

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